Mark Collard

Investigating cultural evolution through biological phylogenetic analyses of Turkmen textiles

The debate on the evolution of culture has focused on two processes in particular, phylogenesis and ethnogenesis. Recently, it has been suggested that the latter has probably always been more significant than the former. This proposal was assessed by applying cladistic methods of phylogenetic reconstruction to a data set comprising decorative characters from textiles produced by Turkmen tribes since the 18th century. The analyses focused on two periods in Turkmen history: the era in which most Turkmen practised nomadic pastoralism and were organised according to indigenous structures of affiliation and leadership; and the period following their defeat by Tsarist Russia in 1881, which is associated with the sedentarisation of nomadic Turkmen and their increasing dependence on the market. The results indicate that phylogenesis was the dominant process in the evolution of Turkmen carpet designs prior to the annexation of their territories, accounting for c.70% of the resemblances among the woven assemblages. The analyses also show that phylogenesis was the dominant process after 1881, although ethnogenesis accounted for an additional 10% of the resemblances among the assemblages. These results do not support the proposition that ethnogenesis has always been a more significant process in cultural evolution than phylogenesis.

Ontogeny and homoplasy in the papionin monkey face

SUMMARY Recent molecular research has provided a consistent estimate of phylogeny for the living papionin monkeys (Cercocebus, Lophocebus, Macaca, Mandrillus, Papio, and Theropithecus). This phylogeny differs from morphological phylogenies regarding the relationships of the mangabeys (Cercocebus and Lophocebus) and baboons (Mandrillus, Papio, and Theropithecus). Under the likely assumption that the molecular estimate is correct, the incongruence between the molecular and morphological data sets indicates that the latter include numerous homoplasies. Knowledge of how these homoplasies emerge through development is important for understanding the morphological evolution of the living papionins, and also for reconstructing the phylogenetic relationships and adaptations of their fossil relatives. Accordingly, we have used geometric morphometric techniques and the molecular phylogeny to investigate the ontogeny of a key area of morphological homoplasy in papionins, the face. Two analyses were carried out. The first compared allometric vectors of Cercocebus, Lophocebus, Macaca, Mandrillus, and Papio to determine which of the facial resemblances among the genera are homoplasic and which are plesiomorphic. The second analysis focused on early post‐natal facial form in order to establish whether the facial homoplasies exhibited by the adult papionins are to some degree present early in the post‐natal period or whether they develop only later in ontogeny. The results of our analyses go some way to resolving the debate over which papionin genera display homoplasic facial similarities. They strongly suggest that the homoplasic facial similarities are exhibited by Mandrillus and Papio and not by Cercocebus and Lophocebus, which share the putative primitive state with Macaca. Our results also indicate that Mandrillus and Papio achieve their homoplasic similarities in facial form not through simple extension of the ancestral allometric trajectory but through a combination of an extension of allometry into larger size ranges and a change in direction of allometry away from the ancestral trajectory. Thus, the face of Mandrillus is not simply a hypermorphic version of the face of its sister taxon, Cercocebus, and the face of Papio is not merely a scaled‐up version of the face of its sister taxon, Lophocebus. Lastly, our results show that facial homoplasy is not restricted to adult papionins; it is also manifest in infant and juvenile papionins. This suggests that the homoplasic facial similarities between Mandrillus and Papio are unlikely to be a result of sexual selection.

Phylogenetic analyses of behavior support existence of culture among wild chimpanzees

Culture has long been considered to be not only unique to humans, but also responsible for making us qualitatively different from all other forms of life. In recent years, however, researchers studying chimpanzees (Pan troglodytes) have challenged this idea. Natural populations of chimpanzees have been found to vary greatly in their behavior. Because many of these interpopulation differences cannot be readily explained by ecological factors, it has been argued that they result from social learning and, therefore, can be regarded as cultural variations. Recent studies showing social transmission in captive chimpanzee populations suggest that this hypothesis is plausible. However, the culture hypothesis has been questioned on the grounds that the behavioral variation may be explained at a proximate level by genetic differences between subspecies. Here we use cladistic analyses of the major cross-site behavioral data set to test the hypothesis that the behavioral differences among the best-documented chimpanzee populations are genetically determined. If behavioral diversity is primarily the product of genetic differences between subspecies, then population data should show less phylogenetic structure when data from a single subspecies (P. t. schweinfurthii) are compared with data from two subspecies (P. t. verus and P. t. schweinfurthii) analyzed together. Our findings are inconsistent with the hypothesis that the observed behavioral patterns of wild chimpanzee populations can be explained primarily by genetic differences between subspecies. Instead, our results support the suggestion that the behavioral patterns are the product of social learning and, therefore, can be considered cultural.

The changing face of genus Homo

Since its introduction in the 18th century, the genus Homo has undergone a number of reinterpretations, all of which have served to make it a more inclusive taxon. In this paper, we trace this trend towards greater inclusiveness, and explain how it has affected the way Homo is defined. We then demonstrate that the current criteria for identifying species of Homo are difficult, if not impossible, to operate using paleoanthropological evidence. We discuss alternative, verifiable, criteria, and show that when these new criteria are applied to Homo, two species, Homo habilis and Homo rudolfensis, fail to meet them. We contend that the lowest boundary of Homo should be redrawn so that the earliest species in the genus is Homo ergaster, or early African Homo erectus. The appearance of this species at around 1.9 Myr appears to mark a distinct shift in hominin adaptive strategy involving morphological and behavioral innovations.

Soft-tissue anatomy of the extant hominoids: a review and phylogenetic analysis

This paper reports the results of a literature search for information about the soft‐tissue anatomy of the extant non‐human hominoid genera, Pan, Gorilla, Pongo and Hylobates, together with the results of a phylogenetic analysis of these data plus comparable data for Homo. Information on the four extant non‐human hominoid genera was located for 240 out of the 1783 soft‐tissue structures listed in the Nomina Anatomica. Numerically these data are biased so that information about some systems (e.g. muscles) and some regions (e.g. the forelimb) are over‐represented, whereas other systems and regions (e.g. the veins and the lymphatics of the vascular system, the head region) are either under‐represented or not represented at all. Screening to ensure that the data were suitable for use in a phylogenetic analysis reduced the number of eligible soft‐tissue structures to 171. These data, together with comparable data for modern humans, were converted into discontinuous character states suitable for phylogenetic analysis and then used to construct a taxon‐by‐character matrix. This matrix was used in two tests of the hypothesis that soft‐tissue characters can be relied upon to reconstruct hominoid phylogenetic relationships. In the first, parsimony analysis was used to identify cladograms requiring the smallest number of character state changes. In the second, the phylogenetic bootstrap was used to determine the confidence intervals of the most parsimonious clades. The parsimony analysis yielded a single most parsimonious cladogram that matched the molecular cladogram. Similarly the bootstrap analysis yielded clades that were compatible with the molecular cladogram; a (Homo, Pan) clade was supported by 95% of the replicates, and a (Gorilla, Pan, Homo) clade by 96%. These are the first hominoid morphological data to provide statistically significant support for the clades favoured by the molecular evidence.

Sexual dimorphism and facial growth in papionin monkeys

Sexual dimorphism in the primate face has been studied intensively lately, but a number of issues remain controversial. For example, some studies have indicated that facial sexual dimorphism arises through ontogenetic scaling, whereas others have found it to be a consequence of both ontogenetic scaling and divergence in male and female growth trajectories. To shed further light on primate facial sexual dimorphism, geometric morphometric methods were applied to crania representing five papionin genera: Cercocebus, Lophocebus, Macaca, Mandrillus and Papio. A first set of analyses focused on the pattern and degree of facial sexual dimorphism exhibited by adult specimens. A second set of analyses concentrated on the ontogeny of facial sexual dimorphism in infant-to-adult age series. The first set indicated that the five genera exhibit significant facial sexual dimorphism. These analyses also revealed that the genera share several features of sexual dimorphism. Males are distinguished from females in having a more prognathic mid-face, a relatively more inferiorly and anteriorly positioned prosthion, relatively increased subnasal height and relatively broader zygomatic roots. They are also differentiated from females in their maxillae, which relative to the zygomatics are narrow but vertically deep, especially in the posterior aspect. Also, the first set of analyses indicated that Macaca is the most distinctive of the genera in terms of sexual dimorphism. The distinctive features of the Macaca sexual dimorphism are that males exhibit relatively wider nasal apertures and premaxillae than females, together with a relative increase in breadth across the inferior zygomatic roots. The second set of analyses demonstrated that in all the genera, sexual dimorphism arises partly through ontogenetic scaling and partly through a late divergence in male and female growth trajectories. The analyses also indicated that the relative contribution of these processes to sexual dimorphism varies among the genera. Ontogenetic scaling is by far the most important process in Lophocebus and Papio. Late divergence between male and female growth trajectories contributes proportionately more in Cercocebus and Mandrillus, although ontogenetic scaling still plays the major role. The relative contribution of late divergence between male and female growth trajectories is greatest in Macaca, in which it accounts for about half of the facial differences between adult males and females. In all five genera, ontogenetic scaling results in increased prognathism and greater relative maxillary size in males compared to females, whilst the late divergence involves the male mid-face becoming proportionately larger and deeper than the female mid-face, and the male posterior maxilla coming to lie more inferiorly with respect to the zygomatic root than its female counterpart.

Population size as an explanation for patterns in the paleolithic archaeological record: more caution is needed

Recently it has become commonplace to use population size to explain patterns in the Paleolithic archaeological record. Several modeling studies support the idea that population size can affect cultural evolution, but the results of empirical studies are ambiguous. Here we report a study that used tool kit data from recent hunter-gatherers, in conjunction with correlation analysis and a global sample, a continental sample, and a regional sample. The results of the analyses do not support the hypothesis. Population size was correlated with some tool kit variables in the global sample, but these relationships disappeared when two factors that have previously been found to affect hunter-gatherer tool kits—risk of resource failure and mobility—were controlled for. Population size was not correlated with the tool kit variables in the other samples. The regression analyses also did not support the population size hypothesis. Together, these results challenge the use of population size to explain patterns in the Paleolithic archaeological record. Population size may explain some of the patterns in question, but this needs to be demonstrated through tests in which the population size hypothesis is explicitly pitted against competing hypotheses, such as adaptation to shifting ecological conditions.

The cophylogeny of populations and cultures: reconstructing the evolution of Iranian tribal craft traditions using trees and jungles.

Phylogenetic approaches to culture have shed new light on the role played by population dispersals in the spread and diversification of cultural traditions. However, the fact that cultural inheritance is based on separate mechanisms from genetic inheritance means that socially transmitted traditions have the potential to diverge from population histories. Here, we suggest that associations between these two systems can be reconstructed using techniques developed to study cospeciation between hosts and parasites and related problems in biology. Relationships among the latter are patterned by four main processes: co-divergence, intra-host speciation (duplication), intra-host extinction (sorting) and horizontal transfers. We show that patterns of cultural inheritance are structured by analogous processes, and then demonstrate the applicability of the host–parasite model to culture using empirical data on Iranian tribal populations.

The acheulean handaxe: More like a bird's song than a beatles' tune?

The goal of this paper is to provoke debate about the nature of an iconic artifact—the Acheulean handaxe. Specifically, we want to initiate a conversation about whether or not they are cultural objects. The vast majority of archeologists assume that the behaviors involved in the production of handaxes were acquired by social learning and that handaxes are therefore cultural. We will argue that this assumption is not warranted on the basis of the available evidence and that an alternative hypothesis should be given serious consideration. This alternative hypothesis is that the form of Acheulean handaxes was at least partly under genetic control.

Palaeoanthropology: Our newest oldest ancestor?

These are exciting times in the study of human origins. But excitement needs to be tempered with caution in assessing the claim of a six-million-year-old direct ancestor of modern humans.